Anyone know how to access Capacitors on a Walkman WM-3?

I managed to get my walkman to work again however the motor stops after a few seconds which I think is due to a capacitor issue however I can only access the back of the walkman where the pulleys and belts and circuit board traces and wiring are. I cant get to the actual electronic components side. The only way I can see so far is by unscrewing the pcb and removing it but as I said theres wiring soldered to it so ill sever all the wiring from the pcb.

I tried looking at the service manual but its like it was written in Klingon (A-Level physics you have failed me) it only really told me how to access the back of the walkman which i already can. Does anyone know how??

 

Ok I found a capacitor does anyone know what would be wwrong with it?

 

OK guys I managed to get a look at all tthe capacitors underneath the main board although I don't know how to judge which is faulty so can someone see in the image below?


There seems to be orange stuff on two of them could that mean it's leaking?

 

Never mind I found a way I can use my digital multimeter and the service manual schematics to test if each capacitor works.

 

The yellow stuf on the light blue ones looks to be glue to stop them wobbling about. Look for signs of dried out liquid around the top or bottom. Because a Walkman is a low power device failure is likely to be far more subtle than on a high power device like a computer Motherboard where the capacitors can literally explode.

 

Very unlikely for bad caps to cause motor shut off- your problem is elsewhere.

 

I also have this problem with my WM-3 but sadly I've not been able so fix it so far. Out of curiosity (and lack of in-depth electronic knowledge) I've tried to change the motor electronics board (the one on top) from a donor unit, and still the problem persists (to be noted that the donor board was untested, so no guarantees that it's not faulty as well. But these walkmans are very well made, and I've successfully bring many from total death, so I gather that the possibility that both boards are faulty to be very slim). I've yet to tinker with the other 2 boards, though...

I too thinked that it may be a capacitor problem, as on my unit the problem seems to have something to do with some components "charging". The motor stops after a few seconds, and when I press stop and play again it will be on again but stops more quickly. If I left the unit off for a while and play it again, it will return to it's original running time of a few seconds.

 

Oh my God thank you it's such a relief to find someone else who has the same problem I've been looking everywhere for someone else with the same issue. And you're absolutely right about the running time.

If I leave it for a while then press play it runs for 8-9 seconds. Then if I stop and play immediately after it only runs for 3 seconds. Then if I leave it for a while then play it returns back to a running time of 8-9 seconds. There has to be something we're not seeing.

 

Do you know of any other possible reasons it could be doing this? If I stop using it for a while and then press play it runs for 8-9 seconds then stops then if I try to stop and play again immediately afterwards it only runs for 3 seconds if that helps. Can the motor not hold power?

 

I did a voltmeter reading on some capacitors on the main board with the Walkman switched on, after the motor stops spinning and their Voltage (measured with a range/limit of 2V) and the capacitors voltage usually remains constant at 1. Something V.

Is that normal doesn't that mean it's not discharging shouldn't it go high than low?

 

Never mind guys I solved the problem My motor works again

 

How did you fix it?

 

Ahhh I just popped Queens Best hits in the walkman and it was so beautiful Finally I got a working walkman!

 

Can i borrow your cassette for a week? some of my walkmans don't work at all. So I wanna play your miracle cassette in those walkman to fix them

 

Sorry for replying so late. It took a shit ton of reading schematics and research I'm not sure if what I'm saying I'd theoretically correct but this is how I solved it. If we look at the service manual we can see there's an area on the Servo Amp PCB dedicated to driving the motor:




The problem wasn't the capacitors but rather faulty transistors. The PCB next to the motor is the Servo Amp board what this mean is that it uses an inductor (electromagnet) that takes in electricity from the power supply of the IC chip and basically converts it into a form of energy that is able to give motion to objects such as linear or circular this is how the Motor works and gets its circular motion.

Now for the "Amp" bit in Servo Amp which stands for amplifier we know that transistors can be used to collect and amplify current in a circuit aswell as be used as a switch. Below is how the motor and the inductor works which I drew on a sticky note lmao because it's hard to read the service manual



Basically the coiled line is our inductor which drives the Motor the current than goes through our transistor to the collector lead. This was where the problem was with my motor. The collector had a voltmeter reading double what the Service manual said it should have which meant that not enough current was going to the base lead to allow the current from the collector to flow through the emitter.

Since the current just remained at the collector there wasn't enough current going back through the inductor to turn the motor. I think that's why my motor would just run for a few seconds when I pressed play and stop as it the current got weaker and weaker. To the point that it just stops.

To test my theory I connected metal leads between the collector and emitter and the motor started turning again.

So to fix it all you have to do is find the solder spots of transistor Q603 using the service manual and bridge the two together so that current flows from the collector straight to the emitter without needing the base to work.

I'm not sure if my theory is 100% accurate though although I managed to fix my motor. And it was very difficult to find anyone else with the same problem so hopefully this helps a lot of people who have the stopping motor problem.

And make sure you bridge the collector and emitter and not the base otherwise the motor won't be as fast as it should and the speed will be inconsistent.

 

Well done in getting that far.

However, the transistor must have been put there for a reason. My guess is that the Servo amp is used to stop the motor speed changing with battery voltage. It is possible that the fault wasn't with the transistor but the circuit driving it. Did you check the voltage on the base ?

If you decide to replace the transistor there are probably hundreds of types that would do the job OK.
Years ago you used to get transistor equivalent books as Japanese, European and American manufacturers all used different numbering systems and within a manufacturers range there would be significant overlap between different parts.

Anyway well done in getting your Walkman playing again.

 

Hold on Scoob you may be onto something. I took a voltmeter reading of the base and it had a value of 0.08-0.09V which wouldn't be enough to let current flow from the collector to the emitter you'd need around 0.6/7v minimum so I revisited the schematics and thought about what you said and I think I know what the problem is. Like the root cause.

I think the problem is the FG component (Function Generator) in the motor. Here's pictures of it below from the Service Manual below:




For those of you that don't know what it does I think Longman was onto something. The Q603 transistor acts as a sort of regulator of current passing through the collector to the emotter, controlled by the IC chip so the motor speed doesn't change with battery voltage and remains constant

Now what the FG does is when the motor spins the FG makes an electrical waveform of the motor current while producing it's own waveform. These two waveforms are sent to the IC one of the motor one of the FG.

It is then sent to the "Comparator" segment of the IC chip this is where it checks the motors waveform against the FG to make sure the motor is moving at the right speed:



Then as you can see above next comes the DC Amp stage where the IC chip sends the appropriate amount of current to make sure the motor moves at the right speed, to the Q603 transistor .



Thus allowing current to flow from the collector to the emitter and turn the motor.


I think that it's possible over time the FG may stop working maybe due to the oil of the motor or age I don't know there's probably like a million reasons maybe there's a way to fix it I'm not sure I'm gonna try to see. Although my theory of the FG being the problem may be wrong.

 

Guys just did a voltmeter reading of the FG and IC entry pins 1 and 2 and it shows as 0V and the service manual says they should be 1.3V each I think we've found the issue it's definitely the FG. The problem is now I think it's inside the motor itself so I don't know how we'll get to it lol.

 

You know what screw it I'm gonna have to take the risk and open up the motor wish me luck I've heard many great men have died looking for replacement bids on eBay.